Can. 1547 Proof by means of witnesses is allowed
under the direction of the judge in cases of any kind.

Can. 1548 §1. When the judge questions witnesses
legitimately, they must tell the truth.

§2. Without prejudice to the prescript of
⇒ can. 1550, §2, n. 2, the following are exempted from
the obligation to respond:

1/ clerics regarding what has been made known to
them by reason of sacred ministry; civil officials, physicians, midwives,
advocates, notaries, and others bound by professional secrecy even by reason of
having given advice, regarding those matters subject to this secrecy;

2/ those who fear that from their own testimony ill
repute, dangerous hardships, or other grave evils will befall them, their
spouses, or persons related to them by consanguinity or affinity.